This invention relates to a three-dimensional displacement gauge to be used in a machine tool or a three-dimensional measuring system.
A conventional touch probe to be used in a machine tool can detect whether or not a contact member of the touch probe touches a workpiece carried on a table of the machine tool. This conventional touch probe is of a binary (ON/OFF) nature. When the contact member of the touch probe touches the workpiece, the contact member itself moves a little. This results in a small error. But the conventional touch probe cannot detect this little movement quantitatively so that it cannot correct the small error.
On the other hand, a three-dimensional measuring device for precise use can quantitatively detect three-dimensional displacement of its probe. This three-dimensional measuring device has detecting means such as differential transformers. But this type of device is too expensive and has a large, heavy and complicated structure. The probe has too little rigidity to apply to machine tools, but is suitable for accurate measuring systems if it is carefully handled.
Other problems are chattering and electrical noise caused by electrical contacts and devices such as a differential transformer provided in the probe. To avoid this problem, an optical type probe is provided having resistance to electrical noise.
A conventional optical probe includes a contact member attached to a holder and a light receiving member attached to a spindle head of a machine tool. Any displacement of the contact member is detected by the light receiving member.
In this optical probe, the optical axis must be adjusted prior to operation. Fouling of the optical system causes some trouble. The conventional optical probe cannot detect quantitatively three-dimensional displacement, but can detect only one-dimensional displacement.
Some conventional touch probes are supported in a housing in such a manner that the probe body is set on three convex portions formed on the housing so that the sensitivity varies according to the approaching direction of the probe body toward a workpiece. This results in inaccuracy.
Generally, a touch probe to be adapted to a machine tool need not detect quantitatively three-dimensional displacement, but is sufficient to detect either small displacement in a first direction or small displacement in a second direction perpendicular to the first direction.
Large complicated touch probes have been devised heretofore, which can detect three-dimensional displacement and a suitable to precise measuring systems. But, a touch probe for measurement either small displacement in a first direction or in a second direction perpendicular to the first direction is not yet provided.